There are several reasons why to drill holes in metal larger than 7/16" in diameter with annular cutter bits:

Annular Cutters drill a burr-free finished hole by cutting only the material around the periphery of the hole. This forms a soli...d slug which automatically pops out.•Less time and energy are consumed per hole•Faster feed rates are achieved with more cutting teeth and less tool wear•Lighter, less powerful drilling equipment can be used•Able to drill holes which are difficult or impossible to do accurately with conventional twist drill tooling - with no pre-drilling or step drilling required.